Overweight and obesity are highly significant clinical and public health issues. More than one third of U.S. adults are obese and another third are overweight. Overweight and obesity are associated with increased risk of numerous diseases and poor health outcomes, including diabetes, cardiovascular disease, hypertension, certain cancers, disability, and all-cause mortality. The National Institutes of Health (NIH) and other organizations have published evidence-based guidelines on the identification, evaluation, and treatment of overweight and obesity in adults, but many studies show that primary care clinicians often do not document overweight or obesity or discuss weight management with their patients. Electronic health records (EHRs) have the potential to improve clinicians' diagnosis and treatment of overweight and obesity by providing tools such as reminders and clinical decision support. However, very few EHR-based tools have been developed to address overweight and obesity in adults. In addition, personal health records (PHRs) that allow patients to view and interact with their EHRs may be able to help patients with weight management by assisting with self- monitoring and providing tailored information and feedback, but their use for this purpose has not been explored in depth. The objectives of the proposed research are to develop and evaluate EHR- and PHR-based tools to improve diagnosis and treatment of overweight and obesity in the primary care setting and, ultimately, to reduce weight gain in overweight and obese patients. The specific aims are: 1) to develop EHR-based tools to help primary care clinicians identify, evaluate, and treat patients who are overweight or obese; 2) to conduct a randomized controlled trial to assess the effectiveness of EHR-based tools for the identification, evaluation, and treatment of overweight and obesity in primary care; and 3) to develop PHR-based tools to help patients manage their weight. This research will be conducted within 18 primary care practices at Brigham and Women's Hospital that already have an existing EHR and PHR. This research could have an important impact on the management of overweight and obesity in the primary care setting. EHR-based reminders, alerts, and decision support for clinicians and PHR-based weight management tools for patients have the potential to address overweight and obesity in a broad-reaching and cost-effective manner, making them attractive public health strategies. Conducting this research within primary care practices at Brigham and Women's Hospital will enable us to evaluate the feasibility and effectiveness of such tools in a real-world setting.